Systems for testing materials, for example the weathering and lightfastness of products such as fabric samples, painted panels, and plastics, are presently available, being sold for example by the Atlas Electric Devices Company of Chicago, Ill. Also, such devices are disclosed in Suga U.S. Pat. No. 4,627,287, and Huber et al. U.S. Pat. Nos. 4,843,893 and 5,226,318, for example. Weathering testing devices test the weathering and lightfastness properties of materials and products under closely controlled conditions.
In the natural environment, heat, light, and moisture combine synergistically to cause optical, mechanical, and chemical changes in products which are exposed to outdoor weathering conditions. Typically, the testing apparatus of this invention and the prior art can be used to obtain such weathering data on an accelerated time basis, to permit product manufacturers to gain information as to how their products will stand up to weathering over the months or years.
Typically, a weathering testing apparatus may use air which circulates through the system to control the temperature of samples being tested, so that they are not underheated or overheated by a heater or radiation source which may be present, typically a high intensity plasma lamp such as a xenon lamp. It is desirable for the samples being tested to be exposed to precisely predetermined conditions, to permit more accurate comparison between various testing runs and the like, and so that the weathering conditions provided by a weathering tester can be accurately predetermined and thus recreated when desired for comparison of various samples over the years, and the like.
By this invention, improvements are provided which increase the accuracy of the testing machine of this invention, in that the machine can be used to provide accurately predetermined conditions which are substantially predictable and invariant throughout a run and from run to run, and also in that temperature and other measurements may be more accurately made, even from sensors which are carried on a moving test rack carried in the enclosure of the testing machine.
By this invention more accurate results, with better reproducability, can be obtained concerning the lifetimes of materials and other testing issues.